Image above: The GRAIL mission begins from Launch Complex-17 in the final liftoff from the pad. NASA/Tom Farrar and Tony Gray› Larger Image The twin launch gantries that mark Space Launch Complex 17 bridge the Space Age from the early days when small rockets achieving modest successes made headlines to the modern era of large boosters regularly lofting probes and satellites into precise orbits with little fanfare.

In a time of gigantic launch servicing structures, control rooms and processing facilities spaced miles apart, SLC-17 harkens to the days when all the specialties of a launch team and support staff worked in the same area, most within the same building.

SLC-17, called "17" by those who worked there, is one of the myriad pads at Cape Canaveral Air Force Station in Florida that launched the early rockets made by engineers and technicians who for many missions just tried to get their machines to work right.

But while the other launch sites were abandoned in some cases before the space race even got going in the 1960s, 17 was adapted again and again to work with progressively better rockets and far more advanced spacecraft. Delta IIs soared into Cape skies from 17 until 2011.

The complex's twin launch pads and their mobile servicing towers, the blockhouse that controllers worked out of for decades, a couple of low-slung office buildings plus a processing building are all within a short stroll of each other.

That physical closeness was the key to the launch complex's enormous success, with a roster that includes some launches only days apart.

"These pads are very well laid out, very easy to operate and process on," said Kathy McLaughlin, site manager for 17 and the Delta II for United Launch Alliance, the company that built the Delta II. "You have everybody here, in a single location."

The launch and support teams also were kept trim, something the workers say made everyone operate more effectively.

"There was never a bloated feel to the launch team," said Tim Dunn, currently a launch director for NASA's Launch Services Program who worked at 17 as a guidance engineer for McDonnell Douglas. "It was always a lean operation. Even as a young engineer, I always felt a high level of responsibility."

The launch structures at 17 are being dismantled. NASA turned over its responsibilities for the second pad at 17 in March so the Air Force can finish the demolition. There will not be any more Delta II launches from Florida, though a few more are slated for launch from Vandenberg Air Force Base in California.

The launch complex was not the highest-tech structure by launch pad standards, but it did what it had to do for well over 50 years, and the people who made their livings launching reliable Delta II rockets from it are forever grateful.

"There are people out here who have really made a contribution to history," said Gary Beatovich, NASA's project manager for SLC-17 deactivation.

The first successful NASA launch from 17A came on Aug. 12, 1960, when a Delta put Echo 1 into orbit, the first communications satellite. Rockets lifting off from 17 placed into orbit: the first satellite to relay television signals and phone calls, Telstar 1; the network of Global Positioning System satellites, or GPS, operational today; many planetary probes and numerous weather satellites.

"After we won the GPS launch contract, that was when everything really went crazy," said Randy Long, who served as a propulsion engineer for McDonnell Douglas when the Delta II was selected. The GPS program would see 47 Delta II launches from 1989 to 2009.

The GPS network, which today tells military and civilian users where they are and where they're heading, revolutionized satellite navigation on Earth.

"The GPS launches were close to my heart," said McLaughlin, "because Desert Shield and Desert Storm had just started - my husband was over there - and they used GPS to redraw the maps they had. Now, it's a part of everyday life."

Some of the most notable exploration missions to other worlds also began at 17, including the Mars Pathfinder, Spirit and Opportunity rovers, plus the Spitzer Space Telescope and other observatories. By the time NASA's GRAIL mission to send twin probes into lunar orbit launched Sept. 10, 2011, the complex had racked up more than 300 launches.

"It was a well-oiled machine," said Darren Bedell, who was NASA's Mission Manager for three planetary missions that launched within two months at 17. "We pushed the system pretty hard to turn that around. You launched, go out and look at the pad and start fixing the pad and four or seven days later you put out the next rocket. It just was one after another after another. There was no hesitation when it came to turning around the pad."

Such a record was not to be expected judging from the first liftoff from 17, a Thor intermediate-range ballistic missile launched Jan. 25, 1957. The missile, making the first flight of the program, hit a high point six inches above the concrete launch stand of 17B before falling through the bottom. The missile hit the flame deflector and exploded in one of the more memorable images from the developmental days of rocketry.

Engineers made their fixes and the Thor line became the first operational missiles of their kind. Meanwhile, rocket designers steadily added stages, upgraded engines, and new solid rocket motors to the Thor, launching major missions along the way.

"It was very positive work," said Wayne McCall, who began working with the program as an electrical engineer for Douglas Aircraft Co., maker of the Thor and retired as NASA's chief of Launch Operations at 17. "There was an enormous amount of work and an enormous amount of technical problems to be solved and we solved a lot of them."

McCall noted that the earliest rockets were guided by systems primitive by today's standards.

"The Thor first stage and the second stage flight controllers still had vacuum tubes in them, since transistors had not entered the mass manufacturing stage yet," he said.

Several of the earliest Pioneer missions to study the moon began on Thor rockets, including Pioneer 5 in 1960 that studied the space between Venus and Earth. Modified Thors and Deltas operated from 17 through most the 1960s until Thors gave way to the Delta rocket, which boasted heavier lifting abilities with a new engine and improved boosters.

"We kept getting pressure to grow the Delta," McCall said. "In the 1970s, we saw the demand to launch bigger satellites to geosynchronous orbit. Our capability to put into geosynchronous orbit (22,300 miles above Earth) was about 70 pounds. So we started strapping solid motors to the boosters, first three, then six, then nine then bigger motors. By strapping those on, that gave us a real boost in capability and we could do 1,500 to 1,800 pounds into geosynchronous orbit."

NASA delivered numerous scientific satellites into orbit to study the sun, Earth, and the region between the planets. Pioneer 7, launched in 1966, measured elements in Halley's Comet 20 years later, discovering a specific form of plasma from the comet.

A series of communications satellites for Indonesia provided McCall one of his brightest career moments, he said. Since Indonesia is made up of about a thousand inhabited islands, building a conventional communications network was proving challenging.

"We tied that country together with satellites," McCall said. "To see the impact on that culture was very pleasurable."

In those years, NASA managed Launch Complex-17 and owned the rockets that flew from it. Like other aspects of the Space Age, that would change. When the Delta II began flying in 1989, NASA began buying launch services for its missions, rather than owning the rockets outright.

The crews of 17 say the launch complex and rocket would not have been so successful without each other. The launchers became workhorses for NASA, the Air Force and commercial satellite builders.

"You've got to have a good rocket to make the pad work, and the Delta II was the best rocket ever," said Steve Seaman, a propulsion engineer for United Launch Alliance.

As the single-stage Thor missiles evolved into the multistage Deltas and then the Delta II and finally the Delta III, the gantries at Pads A and B added levels and layers to keep up, reminiscent of the way a tree grows, with new material added to an older core.

"The pad reflected the rocket," Dunn said. "We would never call Delta simple, we would call it a straightforward rocket. Complex 17 took on that feel as well. Get the pad to where you need it and there's no reason to go beyond that."

The launch complex also holds the distinction of being the last operational complex that required a person to push a button to launch a rocket. While other pads went to a computerized auto-sequencer, such as the space shuttle used, 17 stayed with a button through 1995. Even then, the only change was from a button push to a mouse click, so there was still a human operator involved.

"If you didn't push that button, it didn't launch," said Bill Hodge, an electrical engineer at the launch complex.

As demanding as the missions were on the rockets, spacecraft and equipment, the focused nature and quick pace brought the 17 crews together, they said.

"It was hectic, but not dysfunctional," said Tom Mahaney, project manager for the closeout of the complex.

"The team had a lot of passion and pride, loving what they did. Without that, the team would not have been as succesful," McLaughlin said. "It was the dedication that made it work."

The work would not let up for long stretches, sometimes a few years at a time.

"There was the time I remember 10 or 11 launches a year," said Marc Lavigne. "I was still very new there and it just fascinated me. You were like, 'OK, I can't take vacation here, here or here.' Everybody had the same frame of mind: It's good to stay busy. People enjoyed that busyness even though it sometimes took a toll on your personal life."

The reward came on launch day, as soon as the spacecraft reached its proper placement in space, whether that meant orbiting Earth or started on a path into deep space.

"Just to see it launch, to see it all come together is a big, big part of the pride," said John Penna, a propulsion engineer for the pad.

There was one day that stood out for everyone, but for the wrong reason. It was Jan. 17, 1997, when the launch team gathered at its familiar stations in the blockhouse sitting between the two launch pads. Dirt had been piled around and in front of the block building over the years to beef up protection, but it was still in the same location as when the first Thor missile was launched in 1957.

Thirteen seconds after lifting off the pad, the rocket carrying the first of a new series of GPS satellites exploded, sending a shock wave to the ground and splintering the rocket into thousands of pieces that rained down on the launch site for many minutes.

"We saw the vehicle let go and somebody said it wasn't too far up," said Lavigne. "Everybody went under their consoles because the overhead monitors were shaking, and we didn't know if they were going to fall down."

No one was hurt in the aftermath of the explosion, but for subsequent launches the team was moved out of the blockhouse to a control center farther away. Dunn and several others lost their cars to chunks of falling rocket, though.

The launch team, the complex and the rocket recovered quickly and got back to their successful ways.

The launch complex and Delta II soon set a record for most consecutive successful launches and built on that record through its final launch in 2011. At the height of the Delta launch manifest, the average launch rate held at about one a month, a statistic that would be hard to improve on, according to the engineers.

"I don't know that you can do any more than 12 in a year," Bedell said. "In the modern world, nobody did it as fast as the 17 crews."